James’ Blog

Frozen drips

Posted on March 5th, 2007 by James.
Categories: General.

I’ve modified my circuit with a little help from my dad. Now the LED(s) are on a separate circuit with a transistor driving them from the 555 timer output.

My dad lent an oscilloscope and the result is a nice little square wave:

With the oscilloscope hooked up, I’ve been modifying the resistors to try and get a nice short pulse length, so that my drips don’t look too elongated and I think it’s working. My current minimum values (with the potentiometers at their lowest) gives me a 10 millisecond pulse with a 20ms delay. Twiddling the pots I can then raise the pulse and delay up to about a second each, so that should be the accuracy I need 🙂

My only problem now is making something that can drip really quickly.

I’ve had quite a bit of trouble doing this. To experiment I took a small water bottle and cut it in half. I then cut a hole in the lid and mounted a small bit of rubber tubing from an old Lego set. Surprisingly even the tiny Lego tube is way too big. If you just let the water flow it comes out in a thick stream. Next I blocked up the top a bit with a little Lego connector with some blutack in it. This seems to work quite well.. but now I’m not getting quite as many drips as I like. So I’ve got to think of something else… Maybe some kind of spinning wheel in the water stream .. but I think that would just make a lot of splashes, not perfect consistent drips. Perhaps a stepper motor as a water pump?

This is my test setup. Unfortunately that perfect frozen drip in the image is a result of my girlfriends rather expensive camera and her even more expensive flash 😉 But you get the idea of how it should work! What’s quite cool is that in this shot the camera is exposed for 1/125 of a second. Which if my maths is correct, is 8ms.. so my 10ms pulse length should be nearly as sharp as this shot, which would be awesome.

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